Burner structures



Dec. 24, 1968 J. E. Hovls ETAI- BURNER STRUCTURES Filed Aug. 8, 1966 5Sheets-Sheet l F igJ 44llt INVENTORS JAWS E. PKDVIS RQLAND L. PFFMANtheir ATTQRNE YS De@ 24 1.958 J. E. Hovls ETAL BURNER STRUCTURES 3Sheets-Sheet 5 Filed Aug. e. 196e INVENToRs JAMES E. Hows ROLLAND L.HOFFMAN BY L/ their ATTORNEY,`

United States Patent O 3,418,062 BURNER STRUCTURES James E. Hovis,Jefferson Township, Allegheny County, and Rolland L. Hoffman, MountLebanon Township, Allegheny County, Pa., assignors to Bloom EngineeringCompany, Inc., Pittsburgh, Pa., a corporation of Pennsylvania Filed Aug.8, 1966, Ser. No. 571,085 14 Claims. (Cl. 431-350) ABSTRACT OF THEDISCLOSURE There are disclosed means and methods for operating a soakingpit, together with a burner structure for this purpose and for generalutility. The burner structure comprises a body member, means mounted onsaid body member for defining a relatively larger outer ring port and arelatively smaller inner firing port disposed coaxially and inwardly ofsaid outer firing port, first annular air passage means coupled to saidouter firing port in bypassing relation to said inner firing port, fuelpassage means coupled centrally to said inner firing port, secondannular air passage means coupled to said inner firing port andsurrounding said fuel passage means, and valve means coupled to each ofsaid first and said second air supplying means, at least said second airpassage means being so shaped that combustion air passing therethroughforms a confining envelope around fuel passage means in avoidance of thesurfaces of said outer firing port.

The present invention relates to burner structures suitable for use insoaking pit furnaces or the like and to means for operating pitfurnaces, more commonly known as soaking pits.

Pit-type furnaces or soaking pits are widely used throughout the steelindustry for heating ingots of steel to rolling or forging temperatures.Although obviously not limited thereto, the apparatus and method of theinvention will be exemplified in connection with firing and operatingsoaking pits for heating steel ingots or slabs to rolling temperatures.

In the conventional operation `of a soaking pit, the steel in gots to beheated for the aforementioned purpose usually are positioned in spacedrelation in the soaking pit chamber, and the pit is provided with aremovable top cover to permit the entry and removal of ingots bysuitable ingot handling apparatus. When the soaking pit has been chargedwith ingots, the cover is positioned upon the coping or rails at the topof the soaking pit, and a combustion system is operated to deliver fluidfuel and combustion air into the soaking pit. In conventional practice,one or more burners are employed to introduce the fuel and combustionair at a relatively high velocity, which fills the soaking pit chamberwith flames and hot products of combustion.

In most instances, the soaking pit is of elongated construction and theone or more burners are located on an end wall of the pit. Accordingly,it is important that the burners be capable, at all times and under alloperating conditions of the soaking pit, of circulating completely anduniformly the hot combustion gases throughout the pit including thespaces between the ingots. A flue duct is coupled to the soaking pit andto a flue system that leads to a suitable exhaust stack. The flow ofcombustion products through the flue system usually is regulated by adamper or the like such that an over-pressure is maintained in thesoaking pit as long as the cover is positioned thereon and while theingots are being heated.

In the usual steel making operation, the ingots are delivered to thesoaking pits at a temperature substantially below rolling temperature,where they are heated and then soaked at a specified rollingtemperature, which may vary Patented Dec. 24, 1968 icc between 2000 F.and 2450" F. The ingots are heated to bring them up to this temperatureand then thermally soaked for an additional period to amelioratetemperature differentials therein. A longer or shorter holding periodmay then follow dependent upon demand for heated ingots at the forge orrolling mill.

A problem then arises from the well-known fact that approximately 6-10times as much fuel and air capacity is required during the heatingperiod to elevate the ingot temperature from the charging temperature tothe ingot rolling temperature than is required near the end of thesoaking period to maintain the soaking pit and the ingots therein at thespecified rolling temperature, after the ingots are brought to thistemperature. In a specific example, the fuel demand can be graduallyreduced to about l0-17% after the soaking pit attains the controltemperature and the ingots reach the rolling temperature. The fueldemand will remain at about lO%-17% of maximum capacity during anysubsequent holding period.

The maximum heating capacity of the soaking pit or furnace is thusestablished by the fuel requirements of the heating portion of thesoaking pit operating cycle. Thus, during the soaking period, it becomesexceedingly diicult, if not impossible with conventional combustionsystem arrangements to maintain a proper circulation of combustion gasesthroughout the soaking pit when the fuel and high velocity combustionair are considerably reduced to the soaking or holding requirements.

In conventional combustion arrangements for soaking pits, as the fueldemand is reduced as set forth above, the heating patterns within thesoaking pit are distorted inasmuch as the combustion systems areprimarily geared to the fuel demand and hot gas circulation requirementsof the heating portion of the cycle. Accordingly, as the soaking portionof the soaking pit cycle is commenced, the necessary reduction in fueldemand foreshortens the hot gas circulation through the soaking pit suchthat the ingots nearer the burner or burners become overheated in orderto maintain the required soaking temperature at the far end of thesoaking pit, i.e., adjacent the end wall of the soaking pit which isopposite from the burner and flue wall. In some cases the top portionsof the nearer ingots begin to melt. The problem becomes more aggravatedwhen the soaking pit is overloaded or is loaded improperly, for example,as in the undesirable, herring-bone pattern.

In one conventional soaking pit heating arrangement a single largeburner is utilized and is so constructed as to operate efficiently as ahigh-velocity burner during the heating portion of the cycle to providea uniform heating and temperature distribution throughout the soakingpit furnace and the ingots therein. However, when the ingots reach theirrequired working temperature, the single, large burner must be turneddown so that it no longer can function as a high-velocity burner, andthe hot combustion gases produced thereby begin to short circuit througha path in the nearer or burner end portion of the soaking pit. As aresult, the nearer ingots become overheated in order to maintain theingots adjacent the far end of the soaking pit at the proper workingtemperature. If the ingots are removed promptly from the soaking pitafter a normal length of soaking under proper loading locations, suchoverheating does not cause any undue difficulties at the rolling mill orin the soaking pit from melting or excessive scaling. In practice,however, the ingots are frequently left for extended holding periodsWithin the soaking pits until the rolling mill or other workingoperations are made ready to receive them. Accordingly, the temperatureat the burner end wall continues to rise, resulting in severeoverheating of the nearer ingots, to the extent that the top portionsthereof begin to melt. or if the control is adjacent the burner end, thefar ingots will be too cold for proper working. In any event, severe andunnecessary losses occur either as a result of the excessive productionof scale at the elevated and prolonged soaking temperatures or of thenecessity for reheating cold ingots.

It has been proposed to operate the single, large burner at a greaterthan minimum fuel requirement for soaking purposes; however, thisresults merely in the extension of the overheated portion of the soakingpit and in increasing the probability of melting the tops of the neareringots. It has also been proposed to operate the burner when on itsminimum heating cycle with a greater percentage of excess combustionair, usually up to 30% excess in contrast to the normal abovestoichiometiic requirements. Although this method alleviates theproblern to some extent, it still does not result in a uniform heatingof the pit during the soaking and holding operations. A furtherdisadvantage lies in the fact that fuel consumption is increased.

These difficulties of the prior art are overcome by the presentinvention, which discloses means of soaking pin operation and burnerarrangements for use therein which involve operation at maximum soakingpit capacity during the heating period, but which involve eicient, highvelocity operation in the neighborhood of 10-17% of maximum pit capacityduring the soaking and holding periods. The heating burner portion ofthe burner arrangement is operated solely during the heating portion ofthe soaking pit cycle, while an associated smaller or auxiliary burnerstructure is operated only during the soaking and/ or hold portion ofthe soaking pit cycle.

The burner structures, moreover, are each constructed or arranged sothat they can discharge hot gases at maximum velocity and heatingeiciency along substantially the entire length of the soaking Ipit inorder to provide a uniform circulation of hot combustion gasesthroughout the pit, during any portion of the soaking pit cycle and atthe widely varying fuel requirements dictated thereby. The unusualresult attained by the disclosed method and apparatus stems from thefact that uniform heating of the soaking pit is attained both during theheating and soaking portions of the operating cycle which has notheretofore been accomplished by known heating arrangements, as statedpreviously.

In one arrangement of the invention, a pair of relatively larger burnersare mounted on the front end Wall of the soaking pit, with each burnerhaving about 50% of rated pit fuel capacity. A soaking and/or holdburner of about 10-17% rated capacity is mounted between the heatingburners for purposes of symmetry. In another arrangement of theinvention, a single, large burner of maximum rated capacity is mountedon one end wall of the soaking pit and a soaking/hold burner similar tothat mentioned in the first example is mounted on the other soaking pitend wall. In the latter example the heating and soaking burners aremounted co-axially or symmetrically in the upper portion of theassociated soaking pit end Wall or walls so as to lie in the mostadvantageous position for uniform circulation of hot gases within thesoaking pit. In either example, the soaking/holding burner is notoperated simultaneously with the heating burner or burners.

In a further arrangement of the disclosed apparatus, the heating ormaximum capacity burner is arranged in a novel fashion Ias an annularstructure surrounding the soaking/hold burner structure, and theconcentric burner structure is mounted on the front end wall of thesoaking pit generally at the location of the single, large conventionalburner mentioned above. Several modilications of the concentric burnerstructure are disclosed herein and are described hereinafter moreparticularly in the forthcoming detailed description of the invention.At this point, however, it should be noted that each section, i.e., theannular maximum capacity section or the inner soaking or hold sectionare each arranged for high-velocity operation at their respective fuelcapacities. More specifically, means are associated with the inner orlow-capacity burner structure for attaining the desired shape of theflame envelope notwithstanding the fact that the concentric burnerstructure is mounted for firing through a single large port in thesoaking pit wall. The concentric burner arrangement is further providedwith novel structure or structures for the inletting of Huid fuel andcombustion air to the respective parts of the burner structure.

It is of interest at this point to compare the resulting gains in flameenergies produced by the method of the invention thus described withsevere reduction in flame energies which have hitherto been encounteredin conventional soaking pit firing arrangements. As an illustration, thefiring of a soaking pit with a single, large high-velocity burner willbe discussed. For purposes of comparison, it will be assumed that theburners have a combustion air velocity of 300 per second. As the burneris turned down from its rated capacity in the heating portion to a fueldemand of 16-17% as determined by the heat required during the soakingportion of the cycle, the combustion air is similarly reduced from 300per second to 50 per second. However, the kinetic energies of therespective flames produced at these operating levels by a single burnerwill vary as the square ofthe ame velocities. Accordingly, the amekinetic energies of the burner at its required lower operating levelduring the soaking period will be only 1/36 that of its rated capacityoperation. This tremendous loss of kinetic energy in the flame isobviously insuflicient to carry the hot burner gases to any greatdistance along the length of a soaking pit. In those soaking pitoperations where the fuel demand during the soaking or holding period iseven less, for example 10% as` is frequently the case, the flame energyof the single large conventional burner is further reduced to only 1/100of full capacity operation of the burner.

During the foregoing discussion various objects, features and advantagesof the invention have -been alluded to. These and other objects,features and advantages of the invention together with structuraldetails thereof will be elaborated upon during the forthcomingdescription of certain presently preferred embodiments of the inventionand of certain presently preferred methods of practicing the same.

In the accompanying drawings, we have shown certain presently preferredembodiments of the invention together with preferred methods ofpracticing the same, wherein:

FIGURE 1 is a top plan View, with parts thereof in section, of a soakingpit and burner structure arranged in accordance with the invention andillustrating one method for operating the soaking pit;

FIGURE 2 is a top plan view, partially sectioned, of another soaking pitand burner arrangement of the invention illustrating another novelmethod of soaking pit operation;

FIGURE 3 is a longitudinally sectioned View of the apparatus as shown inFIGURE 2 and taken along reference line III-III thereof;

FIGURE 4 is a graphical representation of various conditions andproblems associated with a typical conventional soaking pit operation;

FIGURE 5 is a longitudinally sectioned view of one form of burnerstructure arranged in accordance with the invention;

FIGURE 6 is a cross-sectional view of the burner apparatus as shown inFIGURE 5 and taken along reference line VI-VI thereof;

FIGURE 7 is a cross-sectional view of the burner apparatus as shown inFIGURE 5 and taken along reference line VII-VII thereof;

FIGURE 8 is a longitudinally sectioned View of another form of theburner structure of the invention;

FIGURE 9 is a cross-sectional view of the ybur-ner structure shown inlFIGURE 8 and taken along reference line IX-IX thereof; l ,y

FIGURE l0 is alongitudinally sectioned view of still another form of theburner structure of the invention; and

FIGURE ll is a cross-sectional view of the apparatus as shown in FIGUREand taken along reference line XI-XI thereof.

Referring now more particularly to FIGURE l of the drawings, a soakingpit 10 and burner arrangement 12 are illustrated therein inexemplication of one method of operating a soaking pit in accordancewith the invention. Usually a battery of soaking pits, for example 10Aand 10B, portions of which are shown in FIGURE 1, are operated together.A common gas or fuel header 14 is provided for a number of soaking pitswhile flue ducts 16 of a pair of soaking pits are coupled to a singleexhaust stack (not shown). Usually a recuperator structure (not shown)is mounted in each exhaust duct for preheating the combustion airsupplied to the recuperator from a suitable blower. The outlet of therecuperator is coupled to an associated air manifold 18 from which theaforementioned burner arrangement 12, in this example, is supplied byindividual conduits 20. In this example, the burner arrangement 12comprises three burners, 22, 24 and 26, to which fuel, gas or the likeis supplied through a branched conduit system 28, the inlet of which iscoupled through control valve 30 to the fuel header 14.

The soaking pit 10A or 10B in this example is of elongated generallyrectangular construction in plan and t includes masonry side and endwalls 32 and 34, respectively, which are backed up by steel plates andother reinforcing structures in the usual manner. The front or burnerend wall 34a is provided in its lower portion with a flue port 36, asbetter shown in FIGURE 3, through which the soaking pit is coupled toits flue duct 16.

An intermediate burner 24 is positioned centrally in the upper portionof the front end wall 34, with side burners 22 and 26 being locatedclosely adjacent thereto and on the same elevation in this example. Theintermediate burner 24 is utilized in this example as the aforedescribedsoak hold burner and is provided with about -40% of the rated capacityof one of the adjacent burners 22 and 26. The latter burners 22, 26together constitute the heating burner arrangement of the soaking pitfurnace and also together equal the rated heating capacity of the pitfurnace. Desirably, the heating burners 22, 26 are of the same size andconfiguration, The heating burners 22, 26, are preferably utilized aspart of this burner arrangement in order to provide overall llamesymmetry in the soaking pit and uniform heating and circulation of theatmosphere thereof. The heating burners 22, 26 are therefore operatedsimultaneously but only during the heating portion of the soaking pitcycle. When the soaking pit has ybeen brought up to soaking or holdtemperatures, the heating burners 22, 26 are shut off by means of gasvalves 36 and suitable valves (not shown) in the air conduits 20. Atthis time, the central soak hold burner 24 is turned on to maintain thesoaking pit and the ingots therein at the desired rolling or workingtemperature of the ingots.

Irrespective of their size, however, all of the burners 22-26 are of thehigh-velocity type and for example can have a combustion air velocity inthe neighborhood of 300 per second. Accordingly, when the fuel demand ofthe soaking pit is reduced to 10-l7% of the maximum or rated fueldemand, which is dictated by the heating portion of the soaking pitcycle, the combustion air which is then introduced solely through thecentral or smaller burner 24, provides the flame with sufficient kineticenergy to carry the hot gases of the burner 24 substantially along theentire length of the soaking pit in order to ensure cornpletecirculation of the hot combustion gases through the pit, as denoted bycirculation arrows 38 of FIGURE 3.

The same air circulation pattern is thus attained by the smaller burner24 as is engendered -by operation of the larger heating burners 22, 26at their maximum or rated capacities. Referring again to FIGURE 3, whenthe soaking pit is thus operated in accordance with the invention, shortcircuiting of the hot gases, for example as denoted by flow arrows 40 or42, is avoided. The foreshortened circulatory path 42 results in theoperation of conventional soaking pits with a single large burner, whilethe intermediate and equally undesirable foreshortened path 40represents previous attempts to solve this problem through the use ofmultiple burners of equal size.

Referring now to FIGURES 2 and 3 of the drawings, another method ofsoaking pit operation in accordance with the invention is illustrated.In this arrangement, a single large burner 44 of rated soaking pitcapacity is mounted in one end -wall 34a, generally at the locationoccupied by the soaking/hold burner 24 of FIGURE 1. Directly oppositefrom the rated capacity burner 44 a substantially smaller soak/holdburner 24 is mounted. In this arrangement the large high-velocity burner44 and the small high-velocity burner 24 can be mounted directlyopposite from one another, and desirably are so mounted, on the samesoaking pit axis as denoted by reference line III-III. The burners 44and 24' `are supplied with suitable air and fuel conduits, as bettershown in FIGURE 3 of the drawings and are generally similar to thosedescribed in FIGURE 1 with the exception that the air and fuel lines 46and 48 respectively of the soak/hold burner 24 are passed beneath theoor structure 50 of the soaking pit.

As better shown in FIGURE 3, the operation of the larger high-velocityburner 44 during the heating operation includes a soaking pit atmospherecirculation as denoted by ow arrows 38 and is very similar to thepattern described previously and occurring during operation of theheating burners 22 and 26 of FIGURE 1. However, when the soak/ holdburner 24 is operated, after shutting olf the large burner 44, thefurnace atmosphere is circulated more or less diametrically therethroughas denoted by ow arrows 52. However, the kinetic flame energy of thehigh-velocity soak/hold burner 24 is sufficient to substantially fillthe soaking pit 10A with hot combustion gases and thereby to heatuniformly the ingots therein during the soaking or hold period.

Referring now to FIGURE 4 of the drawings, the advantageous results ofthe application of the methods disclosed herein in comparison toconventional or previously proposed methods of operation involving asingle highvelocity burner or a number of correspondingly smaller suchburners of equal sizes. In FIGURE 4, a number of curves are utilized toprovide a comparison between fuel flow and various soaking pit and ingottemperatures. Although the illustrated curves have been somewhatidealized, e.g. to provide smoothness, etc., the curves represent avalid comparison of soaking pit conditions for both conventional anddisclosed methods of operation, respectively. Curve 54 represents acomparison of fuel requirements during charge, heat, soak and holdperiods of the soaking pit cycle. The vertical, dashed line 56 denotesthe optimum time of lingot removal, whereat the ingots are uniformlyheated to the ingot rolling temperature as denoted by curve 58. However,the ingots are frequently left in the soaking pit beyond the idealsoaking period, which is denoted in FIGURE 4, giving rise to a holdingperiod denoted in the graph of FIGURE 4 to the right of the verticalline 56. Curve 60 denotes the control temperature of the soaking pitwhich is slightly higher than the desired rolling temperature.

The plateau 54a of fuel curve 54 denotes the maximum or rated fueldemand of the pit furnace as dictated by the fuel requirements of theheating period. When the pit temperature reaches the controltemperature, as denoted by knee 60a of the curve 60, the fuelrequirement can be then gradually reduced to about 10-17% of ratedcapacity as denoted -by the fuel curve portion 54b. After the ingotshave reached uniform temperatures throughout, the fuel demand remainsduring the hold period at about l0l7% of rated capacity as denoted byfuel curve portion 54e.

In known methods of soaking pit operation wherein the hot soaking pitgases are short circuited either along the nearer circuit 42 or theintermediate circuit 40 (FIG- URE 3), the burner end wall temperatureand the temperature of the nearer ingots continue to rise during thesoaking period as denoted by curves 62 and 64, respectively, when thecontrol sensor is at the far end wall. If the ingots are removed at theend of the soaking period it will be seen that in conventional methodsthat the temperature 'of the front or nearer ingots has not risen undulyas denoted -by the intersection of the curve 64 with the vertical liney56. In an ideal soaking pit operation, therefore, the use ofconventional methods is not particularly disadvantageous.

As pointed out previously, however, the ingots frequently are left inthe soaking pit beyond the ideal soaking period giving rise to theholding portion of the FIG- URE 4 graph. When using conventional methodsof soaking pit operation, the temperature of the soaking pit burner walland of the nearer ingots, or :of the intermediate ingots as the case maybe, continues to rise as denoted lby curves 62 and 64 respectively. Thisrise in the holding period, which limit has not always been ob- ..servedwith the result that the tops of the nearer or intermediate ingotsfrequently have become melted or washed before the ingots are removedfrom the soaking pit to the rolling mill or the like. Furtherdisadvantages stem 'from the fact that the ingots are no longeruniformly heated with reference to the entire charge which, of course,gives rise to well-known difficulties in operating the rolling mill orthe like. Finally, excessive quantities of scale yare produced by theelevated temperatures of the conventional holding period, and theformation of such scale is still further accelerated in unsuccessfulattempts to heat the soaking pit atmosphere more uniformly withconventionally available equipment.

With the operating apparatus of the invention, a uniformly heatedatmosphere is attained within the soaking pit `both during the soakingand holding periods. Furthermore, the consumption of fuel is reducedduring the holding period by eliminating the necessity of usingadditional excess combustion air. The soaking pit operational methodsand the apparatus therefor are arranged such that the front and rear endwall temperatures can `be maintained essentially the same for anindefinite period of time as denoted by curve 60. It follows then thatthe ingot temperature likewise can be held uniformly for an indefiniteperiod of time as denoted by curve 58.

Referring now to FIGURES -7 of the drawings7 another exemplary burnerarrangement is shown therein which is suitable for use in the soakingpit operation of the invention, but which can be used in otherapplications requiring burner structures of differing rated capacities.In the present arrangement, the burner 66 includes a body structure 68which is closed at the 4outlet or llame end by combustion air passagemeans such as a baille structure denoted generally by referencecharacter 70 and fabricated from either refractory or water-cooledstructures. The body 68 can 'be bolted or otherwise secured to a furnacewall 72 by means of its outlet flange 74. When thus secured, the outletof the body structure is aligned with firing port 76 extendingtransversely through the furnace wall 72.

The baille structure 70 includes a first annular baille 78 provided withgenerally longitudinally extending air passages 80 which are, in thisexample, arranged in an equally spaced annular array around the baille78. In this example, six such passages are utilized, although it will beobvious that la greater or lesser number can be employed. Positionedinwardly, and in this example axially, of the'annular baille 78 is. agenerally tubular inner port block 82, the free inner surface 84 ofwhich defines a second firing chamber or port. A second annular baille86, which can be constructed Ias mentioned in oonnection with the baille70, is mounted within the port block 82 adjacent the inner or front endthereof. The second baille 86 is thus likewise provided with an annulararray of air passages 88, which in this example are equally spaced landeight in number, as better shown in FIG- URE 6 of the drawings. It will-be understood, of course, that here too a greater or lesser number ofair passages 88 can be employed depending upon the application of theinvention.

The second or inner annular baille 86, in addition, is provided with acentral fuel port 90 into which a fuel conduit 92 opens. In thisexample, the fuel conduit 92 is mounted concentrically within acombustion air conduit 94 and both thus extend rearwardly through theend wall portion 96 of the body structure 68. The concentric conduits92, 94 respectively terminate in supply fittings 98 and 100. The fuelsupply fitting 100 and the fue] conduit 92 are capable of supplyingsuflicient fluid fuel as required either by the greater quantity ofcombustion air supplied through the outer air passages 82 or by thelesser supply through the inner air passages 88. The outer air passagesare supplied by a separate air inlet 102 coupled to the 'body structure68. The inner air passages 88 are supplied, in this example, through theair conduit 94 and the low flow air fitting 98.

In the operation of the yburner structure as illustrated in FIGURES 5-7of the drawings, it is contemplated that the inner and outer burnersections thereof can 'be operated simultaneously or separately. In thesimultaneous operation, combustion will occur b-oth at the inner firingport 84 and at the outer firing port 76 as the fuel respectively comesin contact with air supplied through the inner air passages 86 and theouter air passages 80. When the apparatus of FIGURES 5-7 is operated inaccordance with the soaking pit operating method of the invention, forexample, it is contemplated that during the heating or maximum fuelcombustion portion of the soaking pit cycle, that high-velocity air willbe emitted to the firing port 76 through the air passages 80 and thatthe low flow air to the inner air passages 88 will be shut .olf byclosing valve 104. The greater quantity of fuel for this stage of theburner operation is supplied by adjusting throttling valve 106 in thefuel line 108.

In order to cause the fuel issuing from the central fuel opening of theinner bale 86 to substantially fill the outer firing port 76, means aremounted within the fuel conduit 92 for imparting a spin to the incomingfluid fuel. One arrangement for thus imparting the spin includes the useof one or more spiral vanes 110 mounted in the fuel conduit 92 adjacentits outlet end, as better shown in FIGURE 5 of the drawings. The spinthus imparted to the incoming fuel enables a llame front to beestablished extending across the entire width of the outer firing port76 adjacent the outer air passages 80. In furtherance of this purposethe air passages 80 desirably are inclined outwardly as shown in thedrawings to cause the air envelope and the expanding and non-burningfuel (when no air is issuing from the inner air passages 88) issuingfrom the inner firing burner 84 to hug the walls or surfaces of theouter firing port 76. On the other hand, the inner fuel passages 88desirably are not inclined so that, when no air is issuing from theouter fuel passages 80, the inner passage air forms a smaller,constricting envelope about the fuel so that the burning fuel-airmixture issues from the inner firing port 84 in `avoidance of the wallsof the outer port 76. At this time, the lower velocity of the fuelpassing through conduit 92, in the arrangement of FIGURE 5, will nothave sufficient spin imparted thereto by the vanes 110 to cause the fuelto disrupt the mu'ch higher velocity air envelope provided by the innerair passages 88.

When it is desired to operate only the inner burner structure, asuitable stop valve (not shown) is actuated to shut olf the air t0 theburner inlet 102 and the low flow air stop valve 104 is opened to supplyair through the inner air passages 88. The smaller cross-sectional areaof the air passages 88 introduces air at substantially the samehigh-velocity into the inner firing port 84, if

desired, 'although the capacity of the inner burner structure issubstantially less than that of the outer burner structure. At the sametime, the fuel throttling valve 106 is turned down to correspondinglyreduce the ow of fuel into the inner firing port 84. As a result,combustion now takes place in the inner firing port 84 anda flame frontis established thereacross adjacent the openings of the inner airpassages 88 and substantially independently of the outer firing port 76.At the considerably reduced ow velocity of the incoming fuel throughfuel conduit 92, the spin imparted by spiral vane or vanes 110 islikewise considerably reduced. Accordingly, the flame envelope does notswell to fill the outer firing port 76 but instead is directed into anelongated configuration by the high-velocity air passing through theinner air passages 88.l With this arrangement then, a high-energy flamecan be produced by either of the outer or inner burner sections althoughthe fuel consumptions differ considerably.

Referring now to FIGURES 8 and 9 of the drawings, a modified form of theburner arrangement of FIGURES -7 is illustrated wherein similarcomponents are denoted by similar reference characters with primedaccents. In the latter arrangement of the invention, outer and innertiring ports 76 and 84 together with outer and inner air passages 80'and 88' are provided, and the air passages `are supplied with combustionair, as described above, with reference to FIGURES 5-7. In thisarrangement, however, a relatively smaller central fuel conduit 92 isutilized solely for supplying fuel to the smaller or inner ring port84'. Accordingly the spiral vanes or other spinning means of FIGURES 5-7are omitted. The fuel for the outer burner section is supplied through asecond, larger fuel inlet 112 extending through the body structure 68'and coupled in communication with an annular fuel conduit 114. The fuelconduit 114 for the outer burner section in turn surrounds the inner endportion of annular air conduit 94 for the inner burner section and thuscommunicates with a plurality of axially extending gas ow grooves 116formed in the outer cylindrical periphery of the inner port block 82. Inorder to 'close the fuel grooves 116 where they are otherwise exposed onthe inward protruding end of the inner port block 82' the annular fuelconduit 114 is extended thereover to a point where it engages the rearface of the outer baie 78.

In the operation of the burner apparatus as shown in FIGURES 8 and 9, ahigh-velocity flame can be produced in the outer tiring port 76 only bysuitably manipulating fuel and air valves 120 and 122, respectively,which are shown schematically in FIGURE 8. In this arrangement of theinvention, it is not necessary to spin the uid fuel when operating theouter burner section inasmuch as the fuel is introduced directly intothe outer firing port 76 in bypassing relation to the inner firing port84 through the fuel passages 116. Where desirable, however, spin can beimparted thereto by canting the fuel grooves 116.

When it is desired to operate the inner burner section only, theaforementioned valves 120 and 122 are shut off and air and fluid fuelare introduced into the inner firing port 84 by suitably manipulatingvalves 104 and 106', respectively. In the latter operation, a highenergyame can be established in the inner tiring port 84' in the same manneras described above with reference to FIGURES 5-7.

" Referring now to FIGURES l0 and 1l of the drawings, still anothermodification of the `burner structure of the invention is illustratedwherein similar components of the preceding figures are identified bysimilar reference characters with primed accents. In burner structure124, the baffle and tiring ports arrangement is substantially similar tothat illustrated and described in connection with FIGURES 8 and 9 of thedrawings. Similarly, the arrangement for supplying high-flow fuel andlow-flow fuel,

respectively to the outer fuel openings 116' and to the inner fuelopening 90' are substantially as set forth previously. The burnerstructure 124 of FIGURES 10 and 1l differs from the burner structure 111of FIGURES 8 and 9 primarily in the manner of supplying combustion airrespectively to the outer air passages 80' and to the inner air passages88. This arrangement of the invention is adapted particularly to supplysuch combustion air through a common throttling valve which can Ibeadjusted to supply such combustion air solely to the outer or to theinner air passages, or in varying amounts to both groups of passageswhen desired.

In this arrangement of the invention, an air conduit 126 extends from anopening 128 in a partition 130 extending transversely across the bodystructure 68 of the burner 124, as better shown in FIGURE ll. The otherend of the air conduit 126 is extended through the annular fuel conduit114', where it engages the inner face of the inner bafe 86' tocommunicate with the inner passages 88', as described above inconnection with FIGURES 8 and 9.

The body partition 130, in this example, also divides the air inlet port132 at the inlet end portion and extends to a Valve mechanism mounted ona shaft, one end of which protrudes through the Wall of the inlet 132 towhich suitable valve operating means (not shown) are secured tomanipulate the valve 134.

In the operation of the invention with the valve 134 disposed in theposition evidenced by chain outline 134a,

combustion air is directed entirely into valve body chamber 138 andthence through conduit 126 to the inner air passages 88'. At the sametime fuel valve 120 is closed and fuel valve 106 is opened to supplyfuel only to the central fuel opening A flame front is thus establishedin the inner firing port 84 as described previously.

When operation only of the outer burner section is desired, the valve134 is moved to its chain outline position 134b so that combustion airis introduced only to burner body chamber 140 from which it ows throughthe outer air passages 80 directly into the outer tiring port 76'. Atthis time, the fuel valve 106 is closed and the fuel valve is opened tosupply fuel through inlet 112 and annular fuel conduit 114 to theannular array of fuel passages 116. In this case, a ame front isestablished in the outer tiring port 76 as noted previously.

Between the extreme positions 134a and 134b of the valve 134, the lattercan be continuously adjusted for the simultaneous operation of bothburner sections with the percentage of maximum or rated `burner capacityin one section being varied inversely with that of the other. rIhus,when the valve 134 is near its closed position 13411, i.e., in its solidoutline position of FIGURE l0, the inner burner section is operated nearits maximum capacity while the outer yburner section is operated nearits minimum capacity. In this case, the fuel throttling valves 106 and120' are accordingly adjusted to supply the appropriate and similarpercentages of maximum fuel ow to the respective burner sections.

It will be understood, of course, that remote valve actuating vmeans canbe coupled to the air valve 134 and to the fuel valves 106 and 120 toproduce corresponding adjustments in the fuel valves 106 and 120', asthe air valve 134 is moved between its extreme positions. It iscontemplated further that similar valve actuating means can be coupledto air Valves 104 and 122' and to fuel valves 106 and 120 of FIGURE 8 orto the similar valves mentioned in connection with FIGURES 5-7, toprovide for similar continuous variation and operation of the inner andouter burner sections of these modifications also.

In order to further exemplify the construction and arrangement of theouter and inner air passages 80 or 80 and 88 or 88 of the burners 66,111 or 124, reference may be had to the air passages arranged asdescribed and claimed in coassigned Patent No. 3,209,808 to Leon F.

1 1 Conway et al., entitled Soaking Pit Burner or the Like, or inco-assigned Patent No. 3,180,394 of Leon F. Conway, entitled Gas Burner.This and other descriptive matter herein, however, is presented solelyfor illustrating the invention and is not limitative thereof.

From the foregoing it wi'l be appreciated that novel apparatus for usein operating soaking pit furnaces and that novel and efficient burnerconstructions have been disclosed herein. It is to be understood,however, that the invention is not limited to the particular applicationillustrated but'that the method and apparatus can be extended to otherapplications involving other types of furnaces. Specifically, itispointed out that the novel iburner structures of FIGURES 5-11 are lnotlimited to soaking pit operations, `but instead can be constructed withdiffering relative fuel capacities of the individual burner sections asrequired for other applications. It will be understood also that theburner sections of each yburner structure can be operated alone orsimultaneously as required and that either or both of the -burnersections of a given burner structure can be operated with higher orlower velocity combustion air than that noted herein depending on theapplication of the invention. Accordingly, while there have been shownand described certain present preferred embodiments of the inventiontogether with present preferred methods of practicing the same, it is tobe distinctly understood that the invention is not limited thereto butmay be otherwise variously embodied and practiced within the scope ofthe following claims.

We claim:

1` A composite burner structure comprising a body member having aforward opening defining substantially an outer firing port, a portblock mounted within said body member, said port block having an openingtherein defining an inner firing port spaced inwardly of said outerfiring port, first combustion air passage means extending through saidport block and disposed laterally outwardly of said inner firing port,said lfirst air passage means communicating with said outer firing portin bypassing relation to said inner port, second combustion air passagemeans and fuel passage means coupled to said port block in communicationwith said inner firing port, and means for supplying fluid fuel to saidfuel passage means and for supplying combustion air to said first andsaid second combustion air passage means, said second air passage meansradially surrounding said fuel passage means and being shaped so thatsaid second air passage means is capable of forming an air envelopesurrounding said fuel to prevent said fuel when combusting within saidinner firing port from filling said outer firing port.

2. The combination according to claim 1 wherein said supplying meansinclude an air chamber defined by said body member and communicatingwith said first air passage means, and said second air passage means andsaid fuel passage means include an annular bafileinserted into theinward end portion of said inner firing port, said baflie having acentral fuel passage and a plurality of air passages disposed radiallyoutwardly of said fuel passage.

3. The combination according to claim 1 wherein said supplying meansinclude a fuel conduit extending into said body member to the fuelpassage means of said inner firing port, and spin means are mounted insaid fuel conduit for imparting substantial spin to fuel flowingtherethrough to said inner firing port upon the velocity of said fuelbeing that required to establish a ame front in said outer firing port.

4. The combination according to claim 1 wherein fuel conduit means arecoupled respectively to said fuel passage means and to a plurality ofgenerally longitudinally extending fuel channels in said port block,said fuel channels extending through said port block and opening intosaid outer firing port in by-passing relation to said inner firing port.

5. The combination according to claim 4 wherein said supplying meansincludes a plurality of coaxial conduits coupled respectively to saidfuel channels, said first an'd said second air passage means, and 'saidfuel passage means. l H

6. The combination according to claim 5` wherein said body member isdivided -by partition means into a" pair of air chambers, one of saidairv chambers being disposed for direct communication with one of saidrst andrsaid' second air passage means, and the other of said air cham-Vbers being coupled to that one of said combustion 'air conduits coupledto the other of said first and said sec'- ond air passage means. `r

7. The combination according to claim 1 vwherein'said port block isbipartite in construction and` includes an outer annular member havingsaid first air passagev means therein and an inner tubular memberclosely fitted With-v in said annular member and extendingv rearwardlythereof for connection to said second air passage means and said fuelpassage means.

8. The combination accolding to claim 7 wherein said port block is ofbipartite construction including an annular member having said first airpassage means therein and a generally tubular member fitted therein andextend# ng rearwardly of said annularv member for connection to saidsecond air passage means and said fuel passage means, said fuel channelsbeing formed Vat least`in part by a like number of grooves formed uponthe outer surface of said tubular member and enclosed by engage?` mentwith said annular member. v

9. The combination according to claim 8 wherein re-V mainders of saidfuel passages are formed by said tubular member grooves and by theadjacent surface of a conduit forming part of said supplying means andinto which the extending portion of said tubular member is closelyfitted.

1G. The combination according to claim 1 wherein said port block is oftripartite construction and includes an outer annular member closelyfitted withinsaid vbody member and having said first air passage meanstherein, a tubular member closely fitted within said oute'annular'member and extending rearwardly thereof, said' tubular member definingsaid inner firing port, and an inner annular member closely fittedwithin the extended portion of said tubular member, said second airpassage means are extended through saidl inner annular member andpositioned radially outwardly of its innery opening, and said fuelpassage means include the central opening of said inner annular member.

11. The combination according to claim 10 whereina plurality ofgenerally longitudinally extending fuel chanf nels are coupled to saidsupplying means and to said outer firing port in by-passing relation tosaid inner firing port, said fuel channels being formed at leastpartially by grooves formed on the outer surface of said tubular memberand enclosed by the adjacent surfaces of said outer annularV member.

12. A- composite burner structure Vcomprising a body member, meansmounted on' said body member forA defining a relatively larger outerfiring port and a relatively smaller inner ring port disposed co-axiallyand inwardly of said outer firing port, first annular lair passage meanscoupled to said outer firing port in lbyypassing relation to said innerfiring port, fuel passagemeansfcoupled generally centrally to said innerfiring port, second annular air passage means coupled to said inner'lfiring portl and surrounding said fuel passage means, and valve meanscoupled to each of said first and said second airv supplying means, atleast said second air passage means being so vshaped that combustion airwhen passing therethrough forms a confining envelope around vfuelissuing from said fuel passage means in avodanceof the surfacesgof saidouter firing port.

13. The combination according to claim 12 wherein said first passagemeans include a plurality of air passages inclined radially outwardly ofsaid burner lbody.

14. The combination according to claim 13 wherein said second airpassage means include a plurality of elongated air passages disposedgenerally parallel to the axis of said inner ring port.

References Cited UNlTED STATES PATENTS 8/1916 Hunter 158-109 10/1942Elder et al. 263-43 5 JOHN I. CAMBY, Primary Examiner.

U.S. Cl. X.R.

